Mechanism for automatic reversing of longitudinal movement of the ribbon on office machines, in particular typewriters



Nov. 28, 1961 A. LEHMAN 3,010,558

MECHANISM FOR AUTOMATIC REVERS LO ITUDINAL MOVEMENT OF THE RIBBON ON OFFICE CH 8, IN

PARTICULAR TYPEWRITERS Filed Nov. 5, 1959 2 Sheets-Sheet 1 i IN VE N TOR A. LEHMANN Nov. 28, 1961 2 Sheets-Sheet 2 Filed Nov. 5, 1959 76 lA/Vf/VTOD: Q A LEKFINDEK LEI-m aw E450 Lea/menu EH/Margaux OF x-won; Lumm/wDrmq. Er a, an, M ,Mfi...

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United States Patent IVIECHANISM FOR AUTOMATIC REVERSING OF LONGITUDINAL MOVEMENT OF THE RIBBON ON OFFICE MACHINES, IN PARTICULAR TYPE- WRITERS Alexander Lehmann, deceased, late of Bischofslreim, Kreis Hanan, Germany, by Elsa Lehmann, ne Elsa Richter, administratrix and sole heir, Fechenheimer Weg 91, Bischofsheim, Kreis Hanan, Germany Filed Nov. 5, 1959, Ser. No. 851,164 Claims priority, application Germany Nov. 7, 1958 Claims. (Cl. 197162)' The invention concerns a mechanism for automatic reversing of the longitudinal movement of the ribbon on ofhce machines, in particular typewriters, where the reverse of the drive for the ribbon spools is effected by means of the ribbon tension exercised on the ribbon reverse levers.

With the existing ribbon reverse systems where the automatic reverse of the ribbon is performed by the ribbon tension exercised on both ribbon reverse levers, the reversing movement resulting fiom tightening of the ribbon at the moment of reverse is initiated by the fact that both the portion of the ribbon deflected forward as well as the portion of the ribbon deflected backward at the same time act on the ribbon reverse lever correlated with the winding-on spool and the winding-off spool respectively. This requires having the ribbon spools arranged forward at a relatively great distance from the platen. This results in a bulky design of the machine. Because of restricted space a placing of these known ribbon reverse mechanisms is therefore not practicable in machines of flat type. Moreover, in machines offlat type the heavily inclined arrangement of the segment and the oblique pull of the ribbon would cause creasing of the ribbon guided in the ribbon center guide.

The object of the invention is to provide an automatic ribbon reverse having ribbon tension, in particular for machines of very flat type, where the ribbon spools are placed close to the platen and the ribbon is guided virtually parallel to the platen, thus obtaining a very compact design for the machine while preventing creasing of the ribbon guided in the ribbon center guide.

According to the invention this is performed in that the ribbon reverse lever correlated with the Winding-on spool and the ribbon reverse lever correlated with the winding-off spool are alternately capable of being automatically blocked or unblocked by a friction pawl depending on the winding direction of the ribbon spools.

As an example an embodiment of the object of the invention is illustrated in the drawings.

FIGURE 1 shows a top view of a typewriter with the mechanism according to the invention,

FIGURE 2 shows a top view of the parts serving for automatic reverse of the longitudinal ribbon movement immediately prior to reversing of the feed from theright hand ribbon drive to the left hand ribbon drive,

FIGURE 3 shows a top view according to FIGURE 2 subsequent to accomplished reversing,

FIGURE 4 is a side view of the left hand ribbon drive of FIGURE 3 viewed in the direction of the arrow A.

To begin with, it should be pointed out that the ribbon drive located on the left side of the machine consists of the same parts as the ribbon drive provided on the right side of the machine. For this reason hereinafter only the ribbon drive provided on the left side of the machine is to be described in detail, and the ribbon drive provided on the right side is to be dealt with only to such extent as is deemed necessary for comprehension of the invention.

On the left side wall 1 of the machine frame thereice 3 and 4) for accommodating the left ribbon drive and on the right side wall 4 of the machine frame likewise by means of screws 5 a support 6 for accommodating the right ribbon drive. A spool shaft 7 is arranged to rotate in a ball bearing 8 (FIG. 4) provided in support 3 and in an angle piece 9 fastened to support 3. Firmly joined to the spool shaft 7 is a ratchet wheel 10, which at the same time serves for accommodating a ribbon spool 11. On the support 3 there is a three-armed rocking lever 12 arranged to pivot around a pin 13. By means of a tipping spring 16 attached on one side to a bend 14 of an arm 15 of the rocking lever 12 and on the other side to the support 3 the rocking lever 12 is capable of pivoting into two terminal positions determined by striking of the bend 14 against a projection 17 or 18 of the support 3.

An additional bend 19 of the arm 15 of the rocking lever 12 is capable of acting together with a ribbon reverser 21 in a manner yet to be described. The ribbon reverser 21 is arranged on the support 3 to pivot around a pin 22. On the support 3 there is moreover a ratchet pawl 24 arranged to pivot around a pin 23. By means of a spring 26 attached to a bend-25 of the ribbon reverser 21 the latter is swivelled counter-clockwise around the pin 22, with the normal position being determined by striking of the ribbon reverser 21 against the pin 23. The other end of the spring 26 is attached to the ratchet pawl 24 and swivels the latter counter-clockwise around the pin 23, thus keeping said pawl engaged with the teeth of the ratchet wheel 10 whenever the rocking lever 12 is located in the position shown in FIG. 3. When the rocking lever 12 is located in the position shown in FIG. 2, then the ratchet pawl 24 is by means of the spring 26 kept in contact with one edge 27 of an arm 28 of the rocking lever 12. In this position of the rocking lever 12 the ratchet pawl 24 is not engaged with the teeth of the ratchet wheel 10. The arm of the rocking lever 12 projecting forward is by means of a link rod 29 joined with the corresponding forward-projecting arm of a rock ing lever 30 of the ribbon drive provided on the right side of the machine.

Between a collar 31 of the ratchet wheel 10 and the balls 32 of the ball bearing 8 (FIG. 4) there is a friction pawl 33 arranged to pivot, which upon rotation of the ratchet Wheel 10 is entrained by friction in one direction or the other. A bend 34 of the friction pawl 33, which engages in a recess 35 of the support 3 and is capable of acting together with a projection 36 of the reverser 21, serves in one position for blocking the ribbon reverser 21 and inanother position for limiting the swivelling movement of the friction pawl 33 during rotation in clockwise direction.

The drive of the ratchet wheel 10 (FIGS. 2 and 3) and thus that of the ribbon spool 11 is eflected by way of a tripping pawl 37, Which is arranged to pivot around a studof a screw 41 screwed to a bend 39 of the support 3. By means of a compression spring 42 provided on the stud of the screw 41 the tripping pawl 37 is either kept engaged by its tooth 43 with the ratchet wheel 10 whenever the rocking lever 12 assumes the position shown' in FIG. 3, or is kept in contact with the edge 27 of the arm 28 of the rocking lever 12 (FIG. 2), whenever the tripping pawl 37 is located in the position of disengage ment from the ratchet wheel 10 by means of the rocking lever 12. By way of a linkage attached to an arm of the tripping pawl 37 and connected with the ribbon oscil' lator bridge, but not illustrated, the tripping pawl 37 is actuated during striking of a key lever. The ribbon 44 is guided along'the platen 20 in the usual manner in-the ribbon center guide 40.

So as to obtain an optimum efiiciency of the ribbon reversing system the arrangement of the mechanism ribbon 44 from the right to the left ribbon spool.

The portion 446 of the ribbon 44 located between the.

wound-full ribbon spool 65, and the ribbon reverser 50 and the portion 44d of the ribbon 44 located between the ribbon reverser 50 and the ribbon center guide 40 on.

the other hand form an obtuse angle resulting in a disadvantageous tension factor. For this reason it is. neces sary in any instance to block the ribbon reverser cor related to the ribbon spool on which the ribbon is being wound. Accordingly reversing of the ribbon is effected by oneribbon reverser only. If'the ribbon 44 is being wound on the ribbon spool 11 the described conditions are reversed.

The alternate unblocking of the wound-full ribbon spool and the blocking of the unwound ribbon spool at the moment of reversing of the ribbon is achieved by the present invention during rotation of the ribbon spools by a friction pawl, as hereinafter described.

For better comprehension of the hereafter described functioning of the invention first of all the position of some parts of the right and of the left ribbon drive is to be briefly described such as is assumed among them iminediatelyprior to the reversing of the drive of the In this process the parts of the left ribbon drive assume the position shown in FIG. 2, in which the friction pawl 33,, which has been rotated clockwise during movement of the ribbon 44 in the direction of the arrow 45 and during rotation of the ratchet wheel around the spool shaft 7, comes to rest with its bend 34 against the edge 46 of the recess 35. In this position the bend 34 of the .frictionpawl 33 is located beyond the path of motion of the projection 36 of the ribbon reverser 21.

Furthermore by means of the edge 27 of the rocking lever 12 the ratchet pawl 24 is kept from engaging with the ratchet wheel 10, thus permittingthe ratchet wheel 10 and the ribbon spool'll to rotate freely. Any overspeeding of the ribbon spool 11 is in this process prevented by a non-illustrated lever which the unwinding ribbon glides past. Moreover, by means of the edge 27 of the rocking lever 12 the tripping pawl 37 is kept from engaging with the ratchet wheel 10, so that said pawl cannot engage with the ratchet wheel 10 during striking of the type keys of the machine.

When in the position shown in FIG. 2, a friction pawl 47 of the right ribbon drive comes to rest with a V bend 48 in front of a projection 49 of the ribbon reverser 50, thus blocking the latter. A ratchet pawl 51 is engaged with a ratchet wheel 52 and keeps the latter in the particular set position. A tripping pawl 53 is in driving connection with the ratchet wheel 52.

If a key is then struck, by the effect of the tension of the ribbon 44 the ribbon reverser 21 of the left ribbon drive is swivelled clockwise around the pin 22 opposing the action of the spring 26. In this procms it acts with a projection 54 on the bend 19 of the arm 15 of the rocking lever 12 and swivels the latter around the pin 13 in clockwise direction. When the ribbon reverser 21 has assumed the position shown in FIG. 2 by means of dotted lines, the rocking lever 12 is under the action of the tipping spring 16 swivelled into the position shown in FIG. 3, which is limitedby striking of the bend 14 7 against the projection 17 of the support 3. During this swivelling the edge 27 of the arm 28 of the rocking lever described, comes to rest against the edge 27 of the arm 28 of the rocking lever 12, is swivelled around the pin 23 4 I in counter-clockwise direction under the action of the spring 26, in the course of which process it engages with the ratchet wheel 10. Furthermore the tripping pawl 37 is under the action of the compression spring 42 engaged with the ratchet wheel 10.

During swivelling of the rocking lever 12 the rocking lever 39 is at the same time by way of the link rod 29 and under the action of the tipping spring 57 swivelled clockwise around the pin 56 into the position shown in FIG. 3. In this process the bend 58 of the rocking lever 30 comes to rest in front of the projection 59 of the ribbon reverser 50. At the same time during swivelling of the rocking lever 30 the edge 61 acts upon the ratchet pawl 51, swivelling the latter contrary to the action of the spring 62 counter-clockwise around the pin 63, with the ratchet pawl 51 thus withdrawing from the tooth system of the ratchet wheel 10 while unblocking the latter. Furthermore by means of the edge 61 of the rocking lever 30 the tripping pawl 53 is withdrawn from the tooth system of the ratchet wheel 52 contrary to the action of the compression spring 64.

Upon striking of one of the type keys the friction pawl 47 is moreover swivelled counter-clockwise during rotation of the ribbon spool 65 of the right ribbon drive by reason of the frictional contact between the collar of the ratchet'wheel 52 and the non-illustrated ball bearing, with the bend 48 of the friction pawl 47 releasing the projection 49 of the ribbon reverser 50.

At the same time as a result of the frictional contact occurring between the collar of the ratchet wheel 10 of the left ribbon drive and the ball bearing 32 the friction pawl 33 is swivelled counter-clcokwise during rotation of the ribbon spool 11. -In this process the said pawl comes to rest with its bend 34 in front of the projection 36 of the ribbon reverser 21, blocking the latter in the position shown in FIG. 3.

Immediately subsequent to accomplished reversing the ribbon reverser 21 is again swivelled back into the position shown in FIG. 2 under the action of the spring 26.

During the subsequent strokes of the type keys the ribbon spool 11 of the left ribbon drive, on which the ribbon 44 is wound, is then blocked and the ribbon spool 65 of the right ribbon drive, from which the ribbon 44 is unwound, is unblocked.

Upon striking of additional type keys, as a result of the ribbon 44 unwinding from the ribbon spool 65 the obtuse angleforrned by the portions 44c and 44d gradually becomes an acute angle, while the acute angle formed by the portions 44:: and 44b gradually becomes an obtuse angle. Once the ribbon 44 is wound on the left ribbon spool 11 and unwound from the right ribbon spool 65, the :abovegdescribed reversing of the ribbon 44 then occurs in the same manner but in inverse sequence.

' By means of the present invention the vibrating of the reversing levers occurringrat the moment of reversing in the usual reversing mechanisms having ribbon tension is furthermore prevented, which otherwise will result in perforation of the ribbon upon striking of the type eys.

1 claim .as my invention:

1. In an ofiice machine having a winding-on spool and a winding-oh spool for a ribbon, a mechanism for automatic reversing of the longitudinal movement of the ribbon comprising a ribbon reversing lever correlated with the winding-on spool, a ribbon reversing lever correlated with the winding-off spool, a ratchet wheel connected to each spool, and afriction pawl engaging each ratchet wheel, said friction pawls being alternately capable of both blocking and unblocking automatically the respective ribbon reversing levers depending on the direction of rotation of the ribbon spools.

2.'A mechanism according to claim 1, in which each ribbon reversing leverconsists of a rocking lever and a ribbon reverser arranged independently of each other.

3. A mechanism according to claim 1, in which a ratchet pawl and a tripping pawl are provided for each ratchet wheel and the ribbon reversing lever correlated with said ratchet wheel includes a rocking lever provided with an edge by means of which the ratchet pawl and the tripping pawl are capable of being engaged with or disengaged from the ratchet wheel.

4. A mechanism according to dlairn 1, in which a ball bearing is provided adjacent each ratchet wheel and the associated friction pawl is arranged between the ball 10 bearing and the ratchet wheel and by means of frictional contact during rotation of the ratchet wheel is capable of arrangement in a position blocking or unblocking the ribbon reversing lever.

5. A mechanism according to claim 1, in which the ribbon spools are arranged close to the platen so that 5 the ribbon is guided substantially parallel to the platen.

References Cited in the file of this patent UNITED STATES PATENTS 1,089,042 Burchett Mar. 3, 1914 FOREIGN PATENTS 252,778 Switzerland Nov. 1, 1948 

